A cell, shunted by a 8 Ω resistance, is balanced across a potentiometer wire of length 3 m. The balancing length is 2 m when the cell is shunted by 4 Ω resistance. The value of internal resistance of the cell will be ____________ Ω. Numerical answer type. Work it out, then open the answer.

Answer: 8. l = l₀R/R+r: 3 = l₀8/8+r, 2 = l₀4/4+r. Dividing: 3/2 = (2(4+r))/(8+r) ⇒ 24+3r = 16+4r r = 8 Ω

A cell, shunted by a 8 Ω resistance, is balanced across a… | JEE Main 2022 (27 Jun, Shift 1)

Q53JEE Main 2022 · 27 JUN · SHIFT 1Medium

Potentiometer

A cell, shunted by a 8 $\Omega$ resistance, is balanced across a potentiometer wire of length 3 m. The balancing length is 2 m when the cell is shunted by 4 $\Omega$ resistance. The value of internal resistance of the cell will be ____________ $\Omega$ .

Numerical answer type. Work it out, then open the answer.

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Answer: 8

$l = l_0\dfrac{R}{R+r}$ : $3 = l_0\dfrac{8}{8+r}$ , $2 = l_0\dfrac{4}{4+r}$ .
Dividing: $\dfrac{3}{2} = \dfrac{2(4+r)}{8+r} \Rightarrow 24+3r = 16+4r$
$r = 8\ \Omega$

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Potentiometer question from JEE Main 2022 (27 Jun, Shift 1)

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